US48531A - dewhubst - Google Patents

Description

RyJ. DBWHURST. SCREW BOLT PoR PASTENING RAILROAD CHAIRS.

NAAsl. Patented July 4,41865 Be it known thatLRICHARD `Hunsnof `the city and county of New York Rioni). JAMES DnwHUns'r. or Nnw YORK, N. Y.

SCREW-BOLT FORAFASTENING RAILROAD-CHAIRS.

Specification of LettersPatent No. 48,531, dated July 4, 1865.

To all whom t may concern JAMES` DEW- other purposes where `the screw is intended to enter and hold in wood; and I do hereby declare that the following4 is a full and eX: l act` description thereof, reference being had to theaccompanying drawings, Figures l and 2, in both of which`` y A is the head of the bolt, here shown of the T form as now generally used for putting down railroad bars and chairs, but it may libe polygonal or of any other form desired. y .iB lis the shank of the `bolt of round bar i iron, and c the screw, which may have any `desired form of thread but the serrated form here` shown `is considered the best `adapted for holding in timber. Thisscrcw `maybe'inade tapering as shown in F ig. l,

" or` `spindle form` or'` cylindrical and gimlet pointed'as shown in Fig. 2.

bolts complete and lit for use by forging the "screw thread thereonwhile hot, by a peculiar `modewhich` I have devised for that My inventionconsists in producing such purpose and by which a rotative and longitudinal movementbeing imparted `to. the bolt, the thread or Ascrewzis gradually formed `and finished, commencing at the` point i of the `bolt and progressing onward to` the required extent: the displaced metal from betweenthe threads being worked into the screw part of the bolt as the operation progresses, thereby` increasing that part of the bolt lengthwise andpreserving a con- Istant and unbroken relationship between the body or central part of the boltand its sursize of iron, its greatercapacity for holding .l y in timber, and the comparative cheapness *Y of its product-ion. The screw thread in these `bolts being produced by forging, `the ma- "terial usually turned off from the `bar to 550;

" `ing `worked intothe screw part of the bolt,

form the thread is ent-irelyeconomized, be-

whichsaving, in a bolt ofthe size shown in i `@the drawings, forms about eighteen per cent.

of the `whole weight.

In relation y to the f matter of strength, it` is well known that iron is not as solid or as strong as the eX- terior portion of such bar, which exterior portion of the bar is usually turned off and wasted, as before observed when the thread is formed by chasing, thus leaving for the body of the screw a portion of the bar which is of inferior strength. In a three quarter inch bolt, as shown in the cylindri- `cal part of C, in Fig. 2, a thread ofproper size to hold efficiently in timber should be cut in to the depth of one eighth of an inch, leaving the central portion half an inch in diameter. The area of the cross section of the bar is thus reduced from .4,417 to .1,963 of a 'square inch, showing that five-ninths of the original substance of the bar has been turned off and wasted in forming the thread, but as before stated, the interior portion thus left to form the body of the screw is of comparatively less strength than the eX- terior portion which was cut away in forming the thread, and although such central portion forms the four ninths of the Msubstance of the bar its strength is not more, in the average run of bar iron, than one third the original strength of such bar: when however', such screw thread is formed by forging, as described, the interior portion becomes consolidated and sostrengthened by the operation as to be equal in ordinary bar iron to about one half the strength Vof such bar; from which it fis manifest that forged screws of a given size of iron are much stronger than chased screws of the same size of iron, thereby enabling such bolts to more eiiciently resist the torsion to which they are unavoidably subjected in penetrating timber.

The tapering form of screw shown in the drawing atFig. l, has also a material advantage over the screw of uniform diameter by reason of the greater hold it takes in the timber, as I have experimentally' ascertained, having placed a chased screw of uniform diameter and a forged screw of tapering form, side by side in the same piece of irc seven per cent. in favor of the taper screwr the mode or process substantially as debolt.

Having thus described my improved screw boltfwhat I claim as my invention, 5 and desire to reoure by Letters Patent is- Tlie bolt with the screw part thereof formed substantially as described and by scribed, as a new article of manufacture.

RICHARD J. DEWHURST.

Witnesses ANDREW I. TODD, JOHN CooHRANE.

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